Ammonia and organic carbon transformation in autogenic continuous flow supercritical water oxidation reactor

Elevated ammonia concentrations in surface waters can be toxic to aquatic life and lead to eutrophication, causing ecological damage and deteriorating water quality. Supercritical water oxidation (SCWO) can potentially be used for ammonia removal. We report on the stability and autogenic operation of the continuous flow SCWO reactor operated with compressed air as a function of auxiliary fuel (ethanol) concentration and preheat temperature. Autogenic SCWO operation was demonstrated without preheating fuel and reagent when the initial ethanol fuel concentration reached 16.13 wt% in the fuel line, enabling the introduction of high mineral content reagents. Ethanol has a synergistic effect on ammonia removal due to elevated concentrations of oxidative free radicals (OH·, HO2·) from hydrocarbon degradation. NH3-N degrades through NH2·, NH·, and HNO to form N2, destruction and removal efficiencies > 99 % for TOC, TN, and NH3-N were achieved at ~560^◦C, ~45 s with 50 % excess air. These data provide insights into SCWO process optimization and scaling potential for treating real-world contaminated wastewater.